Angiography refers generally to the capture and representation of blood vessels or vasculature of the human body by means of X-ray imaging, i.e., X-ray vascular imaging. X-ray diagnostic imaging systems may be used for angiographic imaging procedures such as digital subtraction angiography (DSA), and live fluoroscopic roadmapping. As currently practiced in the art, digital subtraction angiography or DSA is an imaging method used for visualizing blood vessels inside a patient's body that includes injecting a contrast medium bolus that is substantially opaque to X-rays into the blood vessels or vasculature under study as images are acquired by the X-ray diagnostic imaging system. Prior to acquisition of the contrast image, a mask image without contrast is acquired. A difference image is calculated by superimposing upon and subtracting the mask image from the contrast image. Ideally, nothing appears in the difference image other than the image of the blood vessels. Because of the time difference between acquisition of the mask image (no contrast) and acquisition of the contrast-enhanced images, global and periodic motion, fluctuations in the intensity of the X-ray source, scattering by the contrast medium, etc., unwanted artifacts may appear in the differenced or digitally subtracted angiographic image.
DSA is useful in the diagnosis and imaging of various blood vessel disorders, such as arterial and venous occlusions, including carotid artery stenosis, pulmonary embolisms and acute limb ischemia; arterial stenosis, particularly for renal artery stenosis; and cerebral aneurysms and arterio-venous malformations.